Voltage Drop Calculation

Voltage Drop Calculation Considering the worst case scenario where the tenant room is located at the furthest end of the top floor, Max. cable length from Tenant DB to furthest lighting point = 30m Full load = 4.8A (80% of 6A MCB) Cable resistance (1C/1.5mm2) = 25mV/A/m VD,ltg = (25 × 10−3 ) × 4.8 × 30 = 3.6 V 3.6 × 100% 415 = 0.867%

VD,ltg % =

Max. cable length from Tenant DB to power point = 30m Full load = 16A (80% of 20A MCB) Cable resistance (1C/2.5mm2) = 18mV/A/m VD,pwr = (18 × 10−3 ) × 16 × 30 = 8.64 V 8.64 × 100% 415 = 2.082%

VD,pwr % =

Max. cable length from Tenant DB to Metering Panel = 70m Full load = 5kVA = 7A Cable resistance (1C/16mm2) = 2.4mV/A/m VD,tenant = (2.4 × 10−3 ) × 7 × 70 = 1.176 V 1.176 × 100% 415 = 0.283%

VD,tenant % =

Max. cable length from Metering Panel to MSB = 150m Full load = 160A (80% of 200A MCCB) Cable resistance (4C/95mm2) = 0.43mV/A/m VD,MP = (0.43 × 10−3 ) × 160 × 150 = 10.32 V 10.32 × 100% 415 = 2.487%

VD,MP % =

Max. cable length from 11/0.433kV transformer = 50m Full load = 1600A (80% of 2000A ACB) Cable resistance (1C/500mm2) = (0.0515+j0.089) Ω/km = 0.103 Ω/km No. of cables = 3 cables for each phase 2 cables for neutral Impedance for 3 cables in parallel Ztail

1 1 1 −1 =( + + ) Z1 Z2 Z3 1 1 1 −1 =( + + ) 0.103 0.103 0.103 = 0.034 Ω/km

Therefore, voltage drop across the transformer tail cables is VD,txf = 0.034 × 1600 × 50 ÷ 1000 = 2.72 V 2.72 × 100% 415 = 0.655%

VD,txf % =

Therefore, the aggregated percentage voltage drop until final circuit is VDL % = VD,ltg % + VD,tenant % + VD,MP % + VD,txf % = 0.867% + 0.283% + 2.487% + 0.655% = 4.292% VDP % = VD,pwr % + VD,tenant % + VD,MP % + VD,txf % = 2.082% + 0.283% + 2.487% + 0.655% = 5.507%